Can you talk someone into wearing a helmet that really doesn't want to? Probably not, without doing the equivalent of dragging a smoker through a cancer ward. Newbies tend to either think they're bulletproof or they're going to die at any moment and act accordingly - I'd say your friend is of the bulletproof type. Maybe you can arrange to be putting on your helmet when he's putting on his dew rag and casually mention how cool his wife'll think he looks with his brainpan all sunlit, then smile sweetly and ride off into the sunset.
Matt
